/** Returns a lower bound on the number of bytes in the DMA receive buffer.
* Also checks for buffer overrun conditions.
* \param s The USART DMA state structure.
*/
u32 usart_n_read_dma(usart_rx_dma_state* s)
{
s32 n_read = s->rd_wraps * USART_RX_BUFFER_LEN + s->rd;
s32 n_written = (s->wr_wraps + 1) * USART_RX_BUFFER_LEN - \
DMA_SNDTR(s->dma, s->stream);
s32 n_available = n_written - n_read;
if (n_available < 0)
/* This strange and rare case occurs when NDTR has rolled over but the flag
* hasn't been raised yet and thus n_wraps hasn't been incremented in the
* ISR. Simply return 0 this time and the next time this function is called
* (or at some point) the interrupt will have been triggered and the number
* of bytes available in the buffer will be a sane amount. */
n_available = 0;
else if (n_available > USART_RX_BUFFER_LEN) {
/* If greater than a whole buffer then we have had an overflow. */
printf("ERROR: DMA RX buffer overrun\n");
n_available = 0;
s->errors++;
/* Disable and re-enable the DMA channel to get back to a known good
* state */
usart_rx_dma_disable(s);
usart_rx_dma_setup(s, s->usart, s->dma, s->stream, s->channel);
}
return n_available;
}
/** Enable the USART peripherals.
* USART 6, 1 and 3 peripherals are configured
* (connected to the FTDI, UARTA and UARTB ports on the Piksi respectively).
*/
void usarts_enable(u32 ftdi_baud, u32 uarta_baud, u32 uartb_baud, bool do_preconfigure_hooks)
{
/* Ensure that the first time around, we do the preconfigure hooks */
if (!all_uarts_enabled && !do_preconfigure_hooks)
return;
/* First give everything a clock. */
/* Clock the USARTs. */
RCC_APB2ENR |= RCC_APB2ENR_USART1EN | RCC_APB2ENR_USART6EN;
RCC_APB1ENR |= RCC_APB1ENR_USART3EN;
/* GPIO pins corresponding to the USART. */
RCC_AHB1ENR |= RCC_AHB1ENR_IOPAEN | RCC_AHB1ENR_IOPCEN;
/* Assign the GPIO pins appropriately:
*
* USART TX RX Connection
* ----------------------------
* 6 PC6 PC7 FTDI
* 1 PA9 PA10 UARTA
* 3 PC10 PC11 UARTB
*/
gpio_mode_setup(GPIOC, GPIO_MODE_AF, GPIO_PUPD_PULLUP, GPIO6 | GPIO7);
gpio_set_af(GPIOC, GPIO_AF8, GPIO6 | GPIO7);
gpio_mode_setup(GPIOA, GPIO_MODE_AF, GPIO_PUPD_PULLUP, GPIO9 | GPIO10);
gpio_set_af(GPIOA, GPIO_AF7, GPIO9 | GPIO10);
gpio_mode_setup(GPIOC, GPIO_MODE_AF, GPIO_PUPD_PULLUP, GPIO10 | GPIO11);
gpio_set_af(GPIOC, GPIO_AF7, GPIO10 | GPIO11);
usart_set_parameters(USART6, ftdi_baud);
usart_set_parameters(USART1, uarta_baud);
usart_set_parameters(USART3, uartb_baud);
/* FTDI (USART6) TX - DMA2, stream 6, channel 5. */
usart_tx_dma_setup(&ftdi_state.tx, USART6, DMA2, 6, 5);
/* FTDI (USART6) RX - DMA2, stream 1, channel 5. */
usart_rx_dma_setup(&ftdi_state.rx, USART6, DMA2, 1, 5);
chBSemInit(&ftdi_state.claimed, FALSE);
ftdi_state.configured = true;
if (do_preconfigure_hooks) {
/* TODO: Should this really be here? */
if ((RCC_CSR & 0xFF000000) != RCC_CSR_PINRSTF) {
if (RCC_CSR & RCC_CSR_IWDGRSTF)
log_error("Piksi has reset due to a watchdog timeout.");
if (RCC_CSR & RCC_CSR_LPWRRSTF)
log_error("Low power reset detected.");
if (RCC_CSR & RCC_CSR_SFTRSTF)
log_info("Software reset detected.");
log_info("Reset reason: %02X", (unsigned int)(RCC_CSR >> 24));
}
log_info("Piksi Starting...");
RCC_CSR |= RCC_CSR_RMVF;
log_info("Firmware Version: " GIT_VERSION "");
log_info("Built: " __DATE__ " " __TIME__ "");
if (uarta_usart.configure_telemetry_radio_on_boot) {
radio_preconfigure_hook(USART1, uarta_baud, "UARTA");
}
if (uartb_usart.configure_telemetry_radio_on_boot) {
radio_preconfigure_hook(USART3, uartb_baud, "UARTB");
}
}
/* UARTA (USART1) TX - DMA2, stream 7, channel 4. */
usart_tx_dma_setup(&uarta_state.tx, USART1, DMA2, 7, 4);
/* UARTA (USART1) RX - DMA2, stream 2, channel 4. */
usart_rx_dma_setup(&uarta_state.rx, USART1, DMA2, 2, 4);
chBSemInit(&uarta_state.claimed, FALSE);
uarta_state.configured = true;
/* UARTB (USART3) TX - DMA1, stream 3, channel 4. */
usart_tx_dma_setup(&uartb_state.tx, USART3, DMA1, 3, 4);
/* UARTB (USART3) RX - DMA1, stream 1, channel 4. */
usart_rx_dma_setup(&uartb_state.rx, USART3, DMA1, 1, 4);
chBSemInit(&uartb_state.claimed, FALSE);
uartb_state.configured = true;
all_uarts_enabled = true;
}
